1. Field of the Invention
The invention relates generally to antimicrobial compositions containing a C.sub.3 -C.sub.6 alcohol and particularly oral compositions, such as but not limited to liquids, pastes and gels for the prevention and elimination of bad breath as well as for the reduction of oral microorganisms responsible for the development of dental plaque, gingivitis, and tooth decay. A preferred embodiment of the present invention relates to a C.sub.3 -C.sub.6 alcohol-containing, reduced ethanol or ethanol-free mouthwash that is effective in preventing those problems.
2. Description of Related Art
The effectiveness of an antimicrobial composition is dependent upon the ability of the composition to deliver the antimicrobial agent(s) contained therein to the desired microbial target(s). This is particularly so for antimicrobial oral compositions where the exposure time of the target microbes to the antimicrobial agent is generally of a short duration.
Oral compositions, such as mouthwashes, have been used by people for many years for the prevention of bad breath and for the elimination of bacteria and other oral microorganisms that are responsible not only for bad breath but also tooth decay, plaque and gum diseases such as gingivitis and periodontitis. To this end, antiseptic mouthwashes in the past have been designed to clean the oral cavity, provide fresh breath and kill these pathogenic microbes.
The leading antiseptic mouthwash has always contained ethanol at a level of 26.9% by volume, based on the total mouthwash volume (hereinafter referred to as "% v/v"). Ethanol is used both as a delivery vehicle and as a solvent in which the active ingredients, and additives such as astringents, color additives, flavor oils, and the like, can be dissolved and then dispersed into solution. Ethanol also enhances the flavor oil organoleptic cues.
However, the use of high levels of ethanol in consumer health products has been recently challenged from an overall health standpoint. Merely reducing the levels of ethanol in these mouthwash compositions has significant disadvantages. It has been found that lower ethanol levels result not only in a loss in the solubility of the actives and other ingredients in the composition, but there is also a noticeable decrease in the ability of the composition to kill the oral microorganisms responsible for bad breath, plaque and gum disease. This loss in antimicrobial activity is believed to be a result of less favorable antimicrobial agent kinetics due to the reduction of ethanol as a vehicle. Antimicrobial agent kinetics affects the rate at which an antimicrobial agent will diffuse from the delivery system and penetrate the dental plaque matrix. Thus, the delivery system of an antimicrobial composition should provide favorable antimicrobial agent kinetics to enhance efficacy, particularly when a composition, e.g. a mouthwash composition, is only applied for a short duration. Heretofore, fairly high levels of ethanol have been required to provide the desired antimicrobial kinetics, particularly for compositions containing antimicrobially effective amounts of essential oils.
There is a substantial need for the development of oral compositions, such as a mouthwash, having a reduced ethanol delivery system with favorable antimicrobial agent kinetics and in which the antimicrobial agents are completely dissolved so that the composition continues to be effective in the prevention of bad breath, the killing of oral microbes and the resultant penetration, reduction or elimination of plaque and gingivitis. Thymol is a well known antiseptic agent, also known as an essential oil, which is utilized for its antimicrobial activity in a variety of mouthwash preparations. In particular, thymol can be utilized in oral hygiene compositions such as mouth rinses in sufficient quantities to provide desired beneficial therapeutic effects. LISTERINE.RTM.-brand mouthwash is a well-known antiseptic mouthwash that has been used by millions of people for over one hundred years and has been proven effective in killing microbes in the oral cavity that are responsible for plaque, gingivitis and bad breath. Thymol and other essential oils, such as methyl salicylate, menthol and eucalyptol, are active ingredients (e., antimicrobial agents) in antiseptic mouth rinses such as LISTERINE.RTM.. These oils achieve their efficacy although present in small amounts. Without being restricted to any specific theory, it is now believed that the efficacy and taste of antiseptic mouthwashes such as Listerine.RTM. may be due to the dissolution and delivery kinetics of these four active ingredients. Dissolution is also important from an aesthetic point of view since a clear mouthwash solution is certainly preferred by consumers to one that is cloudy, turbid or heterogeneous.
Mouthwash compositions containing ethanol or isopropanol or a mixture of both are known. For example, U.S. Pat. No. 3,947,570 discloses a mouthwash composition having 0.01 to about 1% by weight, based on the total weight of the composition (hereinafter referred to as "% w/w"), of lemon oil flavoring, 0 to about 25, preferably 5 to 24% w/w of a nontoxic alcohol such as isopropanol and ethanol, about 0.1 to 5% w/w of a non-ionic surfactant and 60 to 95% w/w water. The alcohol may be denatured with flavoring agents, generally in an amount between about 1 and 2 percent of the total amount of alcohol in the composition. The disclosed flavoring agents include anethole, anise oil, bay oil, benzaldehyde, bergamot oil, bitter almond, camphor, cedar leaf oil, chlorothymol, cinnamic aldehyde, cinnamon oil, citronella oil, clove oil, coal tar, eucalyptol, eucalyptus oil, eugenol, guaiacol, lavender oil, menthol, mustard oil, peppermint oil, phenol, phenyl salicylate, pine oil, pine needle oil, rosemary oil, sassafras oil, spearmint oil, spike lavender oil, storax, thyme oil, thymol, tolu balsam, turpentine oil, wintergreen oil and boric acid.
U.S. Pat. No. 5,292,528 is directed to an oral composition containing 0.001% to 50% w/w of an organosilicone-type quaternary ammonium salt immobilized in a water insoluble solid cairier and at least one surfactant of either 0.01% to 15% w/w polyoxyethylene-polyoxypropylene block copolymer or 0.001% to 50% w/w of alkoxyamide. The composition may also contain 0.01% to 20% w/w of a thickening agent and preferably at least one alcohol selected fiom the group consisting of ethanol, propanol and isopropanol in an amount of about 0.01% to 60% w/w. This reference exemplifies a composition containing an immobilized quaternary ammonium salt, chlorohexidine gluconate and a mixture of ethanol and isopropanol. The reference also discloses that flavoring agents, such as various essential oils, may be used if desired.
U.S. Pat. No. 4,132,770 discloses a mouthwash composition containing about 3 to 9% w/w baking soda, 0 to about 20%, preferably about 5 to 15% w/w of a nontoxic cosmetic alcohol such as ethanol or isopropanol, about 0.5 to 4.0% w/w of a non-ionic surfactant and 60 to 95% w/w water. The alcohol preferably contains a flavor oil, such as those listed above, in an amount of about 0.05-0.4% w/w.
U.S. Pat. No. 5,302,373 describes a concentrated mouthwash formula having 5 to 50% w/w ethanol, 2 to 30% w/w alkali metal bicarbonate, 0.5 to 30% w/w humectant and 5 to 35% w/w water. The composition may also contain up to about 3% w/w hydrophilic polymer and up to about 5% w/w surfactant. This reference discloses that part or all of the ethanol can be substituted by a nontoxic cosmetic monohydric alcohol, such as isopropanol. Other optional components that may be present in the composition include, among others, thymol, as a bactericide, and flavorants such as oils of spearmint, peppermint, wintergreen, sassafras, clove, sage, eucalyptus, cinnamon, lemon, orange and methyl salicylate. These references do not exemplify or suggest the advantage of employing a C.sub.3 to C.sub.6 aliphatic alcohol with an antimicrobial effective amount of one or more essential oils.
Other prior art references have broadly disclosed, but not exemplified, substituting lower alkyl mono- or dihydric- alcohols for ethanol in various mouthwash formulations. For example, U.S. Pat. No. 5,256,401 describes a mouthwash composition having a water-alcohol mixture with a weight ratio in excess of 10:1 and about 0.01 to about 0.9% w/w of a noncationic antibacterial agent, such as triclosan. The alcohol may be a non-toxic alkyl mono- or dihydric alcohol, such as ethanol, n-propanol, isopropanol or propylene glycol, although only ethanol is exemplified. The prefelTed antimicrobial agents include triclosan, phenol, thymol, eugenol, 2,2-methylene bis (4-chloro-6-bromophenol), nerolidol and bisabolol. The use of the phenolic compounds, however, is not exemplified. It is also disclosed that surface active agents are desirable and that flavor oils may be employed, The antimicrobial is solubilized in a low amount of alcohol by using low concentrations of the antimicrobial in the composition.
Clearly, there is still a need for an antimicrobial composition having a delivery system capable of enhanced antimicrobial agent kinetics so as to provide effective antimicrobial treatment even when the duration of the treatment is short. Moreover, there is a particular need for a reduced ethanol or ethanol-free composition that is highly efficacious in the prevention of bad breath, plaque and gum disease. In addition, there is a need for such oral compositions that both kill the oral microflora responsible for these problems and clean the oral cavity leaving a finesh, lubricous mouthfeel.